/* ----------------------------------------------------------------------
* Copyright (C) 2010-2014 ARM Limited. All rights reserved.
*
* $Date:        19. March 2015
* $Revision: 	V.1.4.5
*
* Project: 	    CMSIS DSP Library
* Title:	    arm_fir_interpolate_f32.c
*
* Description:	FIR interpolation for floating-point sequences.
*
* Target Processor: Cortex-M4/Cortex-M3/Cortex-M0
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
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*     distribution.
*   - Neither the name of ARM LIMITED nor the names of its contributors
*     may be used to endorse or promote products derived from this
*     software without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
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* -------------------------------------------------------------------- */

#include "arm_math.h"

/**
 * @defgroup FIR_Interpolate Finite Impulse Response (FIR) Interpolator
 *
 * These functions combine an upsampler (zero stuffer) and an FIR filter.
 * They are used in multirate systems for increasing the sample rate of a signal without introducing high frequency images.
 * Conceptually, the functions are equivalent to the block diagram below:
 * \image html FIRInterpolator.gif "Components included in the FIR Interpolator functions"
 * After upsampling by a factor of <code>L</code>, the signal should be filtered by a lowpass filter with a normalized
 * cutoff frequency of <code>1/L</code> in order to eliminate high frequency copies of the spectrum.
 * The user of the function is responsible for providing the filter coefficients.
 *
 * The FIR interpolator functions provided in the CMSIS DSP Library combine the upsampler and FIR filter in an efficient manner.
 * The upsampler inserts <code>L-1</code> zeros between each sample.
 * Instead of multiplying by these zero values, the FIR filter is designed to skip them.
 * This leads to an efficient implementation without any wasted effort.
 * The functions operate on blocks of input and output data.
 * <code>pSrc</code> points to an array of <code>blockSize</code> input values and
 * <code>pDst</code> points to an array of <code>blockSize*L</code> output values.
 *
 * The library provides separate functions for Q15, Q31, and floating-point data types.
 *
 * \par Algorithm:
 * The functions use a polyphase filter structure:
 * <pre>
 *    y[n] = b[0] * x[n] + b[L]   * x[n-1] + ... + b[L*(phaseLength-1)] * x[n-phaseLength+1]
 *    y[n+1] = b[1] * x[n] + b[L+1] * x[n-1] + ... + b[L*(phaseLength-1)+1] * x[n-phaseLength+1]
 *    ...
 *    y[n+(L-1)] = b[L-1] * x[n] + b[2*L-1] * x[n-1] + ....+ b[L*(phaseLength-1)+(L-1)] * x[n-phaseLength+1]
 * </pre>
 * This approach is more efficient than straightforward upsample-then-filter algorithms.
 * With this method the computation is reduced by a factor of <code>1/L</code> when compared to using a standard FIR filter.
 * \par
 * <code>pCoeffs</code> points to a coefficient array of size <code>numTaps</code>.
 * <code>numTaps</code> must be a multiple of the interpolation factor <code>L</code> and this is checked by the
 * initialization functions.
 * Internally, the function divides the FIR filter's impulse response into shorter filters of length
 * <code>phaseLength=numTaps/L</code>.
 * Coefficients are stored in time reversed order.
 * \par
 * <pre>
 *    {b[numTaps-1], b[numTaps-2], b[N-2], ..., b[1], b[0]}
 * </pre>
 * \par
 * <code>pState</code> points to a state array of size <code>blockSize + phaseLength - 1</code>.
 * Samples in the state buffer are stored in the order:
 * \par
 * <pre>
 *    {x[n-phaseLength+1], x[n-phaseLength], x[n-phaseLength-1], x[n-phaseLength-2]....x[0], x[1], ..., x[blockSize-1]}
 * </pre>
 * The state variables are updated after each block of data is processed, the coefficients are untouched.
 *
 * \par Instance Structure
 * The coefficients and state variables for a filter are stored together in an instance data structure.
 * A separate instance structure must be defined for each filter.
 * Coefficient arrays may be shared among several instances while state variable array should be allocated separately.
 * There are separate instance structure declarations for each of the 3 supported data types.
 *
 * \par Initialization Functions
 * There is also an associated initialization function for each data type.
 * The initialization function performs the following operations:
 * - Sets the values of the internal structure fields.
 * - Zeros out the values in the state buffer.
 * - Checks to make sure that the length of the filter is a multiple of the interpolation factor.
 * To do this manually without calling the init function, assign the follow subfields of the instance structure:
 * L (interpolation factor), pCoeffs, phaseLength (numTaps / L), pState. Also set all of the values in pState to zero.
 *
 * \par
 * Use of the initialization function is optional.
 * However, if the initialization function is used, then the instance structure cannot be placed into a const data section.
 * To place an instance structure into a const data section, the instance structure must be manually initialized.
 * The code below statically initializes each of the 3 different data type filter instance structures
 * <pre>
 * arm_fir_interpolate_instance_f32 S = {L, phaseLength, pCoeffs, pState};
 * arm_fir_interpolate_instance_q31 S = {L, phaseLength, pCoeffs, pState};
 * arm_fir_interpolate_instance_q15 S = {L, phaseLength, pCoeffs, pState};
 * </pre>
 * where <code>L</code> is the interpolation factor; <code>phaseLength=numTaps/L</code> is the
 * length of each of the shorter FIR filters used internally,
 * <code>pCoeffs</code> is the address of the coefficient buffer;
 * <code>pState</code> is the address of the state buffer.
 * Be sure to set the values in the state buffer to zeros when doing static initialization.
 *
 * \par Fixed-Point Behavior
 * Care must be taken when using the fixed-point versions of the FIR interpolate filter functions.
 * In particular, the overflow and saturation behavior of the accumulator used in each function must be considered.
 * Refer to the function specific documentation below for usage guidelines.
 */

/**
 * @addtogroup FIR_Interpolate
 * @{
 */

/**
 * @brief Processing function for the floating-point FIR interpolator.
 * @param[in] *S        points to an instance of the floating-point FIR interpolator structure.
 * @param[in] *pSrc     points to the block of input data.
 * @param[out] *pDst    points to the block of output data.
 * @param[in] blockSize number of input samples to process per call.
 * @return none.
 */
#ifndef ARM_MATH_CM0_FAMILY

/* Run the below code for Cortex-M4 and Cortex-M3 */

void arm_fir_interpolate_f32(
    const arm_fir_interpolate_instance_f32 *S,
    float32_t *pSrc,
    float32_t *pDst,
    uint32_t blockSize)
{
    float32_t *pState = S->pState;                 /* State pointer */
    float32_t *pCoeffs = S->pCoeffs;               /* Coefficient pointer */
    float32_t *pStateCurnt;                        /* Points to the current sample of the state */
    float32_t *ptr1, *ptr2;                        /* Temporary pointers for state and coefficient buffers */
    float32_t sum0;                                /* Accumulators */
    float32_t x0, c0;                              /* Temporary variables to hold state and coefficient values */
    uint32_t i, blkCnt, j;                         /* Loop counters */
    uint16_t phaseLen = S->phaseLength, tapCnt;    /* Length of each polyphase filter component */
    float32_t acc0, acc1, acc2, acc3;
    float32_t x1, x2, x3;
    uint32_t blkCntN4;
    float32_t c1, c2, c3;

    /* S->pState buffer contains previous frame (phaseLen - 1) samples */
    /* pStateCurnt points to the location where the new input data should be written */
    pStateCurnt = S->pState + (phaseLen - 1u);

    /* Initialise  blkCnt */
    blkCnt = blockSize / 4;
    blkCntN4 = blockSize - (4 * blkCnt);

    /* Samples loop unrolled by 4 */
    while(blkCnt > 0u)
    {
        /* Copy new input sample into the state buffer */
        *pStateCurnt++ = *pSrc++;
        *pStateCurnt++ = *pSrc++;
        *pStateCurnt++ = *pSrc++;
        *pStateCurnt++ = *pSrc++;

        /* Address modifier index of coefficient buffer */
        j = 1u;

        /* Loop over the Interpolation factor. */
        i = (S->L);

        while(i > 0u)
        {
            /* Set accumulator to zero */
            acc0 = 0.0f;
            acc1 = 0.0f;
            acc2 = 0.0f;
            acc3 = 0.0f;

            /* Initialize state pointer */
            ptr1 = pState;

            /* Initialize coefficient pointer */
            ptr2 = pCoeffs + (S->L - j);

            /* Loop over the polyPhase length. Unroll by a factor of 4.
             ** Repeat until we've computed numTaps-(4*S->L) coefficients. */
            tapCnt = phaseLen >> 2u;

            x0 = *(ptr1++);
            x1 = *(ptr1++);
            x2 = *(ptr1++);

            while(tapCnt > 0u)
            {

                /* Read the input sample */
                x3 = *(ptr1++);

                /* Read the coefficient */
                c0 = *(ptr2);

                /* Perform the multiply-accumulate */
                acc0 += x0 * c0;
                acc1 += x1 * c0;
                acc2 += x2 * c0;
                acc3 += x3 * c0;

                /* Read the coefficient */
                c1 = *(ptr2 + S->L);

                /* Read the input sample */
                x0 = *(ptr1++);

                /* Perform the multiply-accumulate */
                acc0 += x1 * c1;
                acc1 += x2 * c1;
                acc2 += x3 * c1;
                acc3 += x0 * c1;

                /* Read the coefficient */
                c2 = *(ptr2 + S->L * 2);

                /* Read the input sample */
                x1 = *(ptr1++);

                /* Perform the multiply-accumulate */
                acc0 += x2 * c2;
                acc1 += x3 * c2;
                acc2 += x0 * c2;
                acc3 += x1 * c2;

                /* Read the coefficient */
                c3 = *(ptr2 + S->L * 3);

                /* Read the input sample */
                x2 = *(ptr1++);

                /* Perform the multiply-accumulate */
                acc0 += x3 * c3;
                acc1 += x0 * c3;
                acc2 += x1 * c3;
                acc3 += x2 * c3;


                /* Upsampling is done by stuffing L-1 zeros between each sample.
                 * So instead of multiplying zeros with coefficients,
                 * Increment the coefficient pointer by interpolation factor times. */
                ptr2 += 4 * S->L;

                /* Decrement the loop counter */
                tapCnt--;
            }

            /* If the polyPhase length is not a multiple of 4, compute the remaining filter taps */
            tapCnt = phaseLen % 0x4u;

            while(tapCnt > 0u)
            {

                /* Read the input sample */
                x3 = *(ptr1++);

                /* Read the coefficient */
                c0 = *(ptr2);

                /* Perform the multiply-accumulate */
                acc0 += x0 * c0;
                acc1 += x1 * c0;
                acc2 += x2 * c0;
                acc3 += x3 * c0;

                /* Increment the coefficient pointer by interpolation factor times. */
                ptr2 += S->L;

                /* update states for next sample processing */
                x0 = x1;
                x1 = x2;
                x2 = x3;

                /* Decrement the loop counter */
                tapCnt--;
            }

            /* The result is in the accumulator, store in the destination buffer. */
            *pDst = acc0;
            *(pDst + S->L) = acc1;
            *(pDst + 2 * S->L) = acc2;
            *(pDst + 3 * S->L) = acc3;

            pDst++;

            /* Increment the address modifier index of coefficient buffer */
            j++;

            /* Decrement the loop counter */
            i--;
        }

        /* Advance the state pointer by 1
         * to process the next group of interpolation factor number samples */
        pState = pState + 4;

        pDst += S->L * 3;

        /* Decrement the loop counter */
        blkCnt--;
    }

    /* If the blockSize is not a multiple of 4, compute any remaining output samples here.
     ** No loop unrolling is used. */

    while(blkCntN4 > 0u)
    {
        /* Copy new input sample into the state buffer */
        *pStateCurnt++ = *pSrc++;

        /* Address modifier index of coefficient buffer */
        j = 1u;

        /* Loop over the Interpolation factor. */
        i = S->L;
        while(i > 0u)
        {
            /* Set accumulator to zero */
            sum0 = 0.0f;

            /* Initialize state pointer */
            ptr1 = pState;

            /* Initialize coefficient pointer */
            ptr2 = pCoeffs + (S->L - j);

            /* Loop over the polyPhase length. Unroll by a factor of 4.
             ** Repeat until we've computed numTaps-(4*S->L) coefficients. */
            tapCnt = phaseLen >> 2u;
            while(tapCnt > 0u)
            {

                /* Read the coefficient */
                c0 = *(ptr2);

                /* Upsampling is done by stuffing L-1 zeros between each sample.
                 * So instead of multiplying zeros with coefficients,
                 * Increment the coefficient pointer by interpolation factor times. */
                ptr2 += S->L;

                /* Read the input sample */
                x0 = *(ptr1++);

                /* Perform the multiply-accumulate */
                sum0 += x0 * c0;

                /* Read the coefficient */
                c0 = *(ptr2);

                /* Increment the coefficient pointer by interpolation factor times. */
                ptr2 += S->L;

                /* Read the input sample */
                x0 = *(ptr1++);

                /* Perform the multiply-accumulate */
                sum0 += x0 * c0;

                /* Read the coefficient */
                c0 = *(ptr2);

                /* Increment the coefficient pointer by interpolation factor times. */
                ptr2 += S->L;

                /* Read the input sample */
                x0 = *(ptr1++);

                /* Perform the multiply-accumulate */
                sum0 += x0 * c0;

                /* Read the coefficient */
                c0 = *(ptr2);

                /* Increment the coefficient pointer by interpolation factor times. */
                ptr2 += S->L;

                /* Read the input sample */
                x0 = *(ptr1++);

                /* Perform the multiply-accumulate */
                sum0 += x0 * c0;

                /* Decrement the loop counter */
                tapCnt--;
            }

            /* If the polyPhase length is not a multiple of 4, compute the remaining filter taps */
            tapCnt = phaseLen % 0x4u;

            while(tapCnt > 0u)
            {
                /* Perform the multiply-accumulate */
                sum0 += *(ptr1++) * (*ptr2);

                /* Increment the coefficient pointer by interpolation factor times. */
                ptr2 += S->L;

                /* Decrement the loop counter */
                tapCnt--;
            }

            /* The result is in the accumulator, store in the destination buffer. */
            *pDst++ = sum0;

            /* Increment the address modifier index of coefficient buffer */
            j++;

            /* Decrement the loop counter */
            i--;
        }

        /* Advance the state pointer by 1
         * to process the next group of interpolation factor number samples */
        pState = pState + 1;

        /* Decrement the loop counter */
        blkCntN4--;
    }

    /* Processing is complete.
     ** Now copy the last phaseLen - 1 samples to the satrt of the state buffer.
     ** This prepares the state buffer for the next function call. */

    /* Points to the start of the state buffer */
    pStateCurnt = S->pState;

    tapCnt = (phaseLen - 1u) >> 2u;

    /* copy data */
    while(tapCnt > 0u)
    {
        *pStateCurnt++ = *pState++;
        *pStateCurnt++ = *pState++;
        *pStateCurnt++ = *pState++;
        *pStateCurnt++ = *pState++;

        /* Decrement the loop counter */
        tapCnt--;
    }

    tapCnt = (phaseLen - 1u) % 0x04u;

    /* copy data */
    while(tapCnt > 0u)
    {
        *pStateCurnt++ = *pState++;

        /* Decrement the loop counter */
        tapCnt--;
    }
}

#else

/* Run the below code for Cortex-M0 */

void arm_fir_interpolate_f32(
    const arm_fir_interpolate_instance_f32 *S,
    float32_t *pSrc,
    float32_t *pDst,
    uint32_t blockSize)
{
    float32_t *pState = S->pState;                 /* State pointer */
    float32_t *pCoeffs = S->pCoeffs;               /* Coefficient pointer */
    float32_t *pStateCurnt;                        /* Points to the current sample of the state */
    float32_t *ptr1, *ptr2;                        /* Temporary pointers for state and coefficient buffers */


    float32_t sum;                                 /* Accumulator */
    uint32_t i, blkCnt;                            /* Loop counters */
    uint16_t phaseLen = S->phaseLength, tapCnt;    /* Length of each polyphase filter component */


    /* S->pState buffer contains previous frame (phaseLen - 1) samples */
    /* pStateCurnt points to the location where the new input data should be written */
    pStateCurnt = S->pState + (phaseLen - 1u);

    /* Total number of intput samples */
    blkCnt = blockSize;

    /* Loop over the blockSize. */
    while(blkCnt > 0u)
    {
        /* Copy new input sample into the state buffer */
        *pStateCurnt++ = *pSrc++;

        /* Loop over the Interpolation factor. */
        i = S->L;

        while(i > 0u)
        {
            /* Set accumulator to zero */
            sum = 0.0f;

            /* Initialize state pointer */
            ptr1 = pState;

            /* Initialize coefficient pointer */
            ptr2 = pCoeffs + (i - 1u);

            /* Loop over the polyPhase length */
            tapCnt = phaseLen;

            while(tapCnt > 0u)
            {
                /* Perform the multiply-accumulate */
                sum += *ptr1++ * *ptr2;

                /* Increment the coefficient pointer by interpolation factor times. */
                ptr2 += S->L;

                /* Decrement the loop counter */
                tapCnt--;
            }

            /* The result is in the accumulator, store in the destination buffer. */
            *pDst++ = sum;

            /* Decrement the loop counter */
            i--;
        }

        /* Advance the state pointer by 1
         * to process the next group of interpolation factor number samples */
        pState = pState + 1;

        /* Decrement the loop counter */
        blkCnt--;
    }

    /* Processing is complete.
     ** Now copy the last phaseLen - 1 samples to the start of the state buffer.
     ** This prepares the state buffer for the next function call. */

    /* Points to the start of the state buffer */
    pStateCurnt = S->pState;

    tapCnt = phaseLen - 1u;

    while(tapCnt > 0u)
    {
        *pStateCurnt++ = *pState++;

        /* Decrement the loop counter */
        tapCnt--;
    }

}

#endif /*   #ifndef ARM_MATH_CM0_FAMILY */



/**
 * @} end of FIR_Interpolate group
 */
